Linear surgical staplers are widely used in surgical operations for wound closure, and internal tissue closure and excision. With the development of the surgical operation, now, people have been more and more inclined to minimally invasive operation. Broadly speaking, a surgery which reduces trauma can be known as minimally invasive operation. While, generally speaking, the minimally invasive surgery is referring to the endoscopic operation in a narrow sense. For the endoscopic surgery, generally, a doctor only needs to open a few of holes and puts surgical staplers used for excision and anastomosis of tissues and auxiliary equipment into the patient's body for surgery through the holes. The trauma of minimally invasive operation brings to the patient is very small and the patient can recover in a short period of time. Therefore, the minimally invasive operation has been paid more and more attention.
U.S. Pat. No. 7,753,246 discloses a linear surgical stapler used in minimally invasive operation, which includes a body portion, and the body portion includes a shell and a firing handle pivotally arranged on the shell, the shell having a relatively movable firing ejector rod therein, the firing ejector rod being able to push the loading unit assembly which located at the front end of the shell to carry out anastomosis and excision. Specifically, the loading unit assembly includes a staple cartridge frame and an anvil pivotally connected with the staple cartridge frame. The staple cartridge frame includes a detachable staple cartridge which includes a series of staple retention holes, generally 4 or 6 rows, accommodating staple pushers and staples. The anvil is arranged with staple forming grooves corresponding to the staple retention holes. The loading unit assembly further includes a movable driver beam arranged in a housing of the loading unit assembly. The driver beam has a knife at the distal end thereof to close the staple cartridge and the anvil when the driver beam is advanced. The knife has a knife blade arranged on its distal central to sever tissues clamped between the staple cartridge and the anvil as the driver beam is advanced. Two wedges are arranged abutting opposite side of the knife blade, that when the knife is advanced, the knife actuates the wedges to push the staple pushers out of the staple cartridge, and the staple pushers sequentially eject staples from the staple cartridge to staple tissues clamped between the cartridge and the anvil.
In the prior art, the loading unit assembly is replaceable from the body portion. When the loading unit assembly assembled on the body portion, the housing of loading unit assembly is inserted into an outer tube distant the staple cartridge. Meanwhile, a lug defined at a proximal end of the driver beam receives in a receiving space located on a distal end of the firing ejector rod; then the loading unit assembly is rotated to engage the housing and tube together and axially fix the driver beam and the firing ejector rod together. After the loading unit assembly fixed to the body portion, a firing of loading unit assembly can be processed subsequently.
After the assembly of the surgical stapler, usually, it needs a long-distance transportation to other places. In the transport process, it is possible that the surgical stapler is shaked or impacted and results in the firing ejector rod is advanced and the staples are fired. Or, after firing of the surgical stapler for the first time, doctors need to replace the loading unit assembly. If the doctor is lack of experience, the loading unit assembly may not be fully installed in place. In the above two cases, if the doctor fires the surgical stapler, that will lead to a serious damage to the surgical stapler, or even cause a medical accident.